Internal combustion engine with gas sealing device

Abstract

An internal combustion engine having a gas sealing device including an L-shaped keystone piston ring groove formed on the outer circumferential surface of a piston, and an L-shaped keystone piston ring in pressing contact with the inner surface of a cylinder and fitted in the L-shaped keystone piston ring groove forming a gap for introducing a gas pressure from a combustion chamber into the piston ring groove. The L-shaped keystone piston ring groove includes an outer groove portion underlying a top land formed in the piston, and a wedge-shaped groove portion contiguous with the outer groove portion and tapering in going toward the center axis of the piston. The L-shaped keystone piston ring includes an outer ring portion disposed in the outer groove portion of the piston ring, and a wedge-shaped ring portion disposed in the wedge-shaped groove portion of the piston ring groove. The top land has a smaller diameter than a second land formed in the piston adjacent the piston ring groove on a side thereof opposite the top land, so that a gap is formed between the top land and the inner surface of the cylinder to communicate with the gap for introducing the gas pressure from the combustion chamber into the piston ring groove.

What is claimed is: 
     
       1. An internal combustion engine comprising a cylinder,   a piston for reciprocating movement arranged in said cylinder,   a combustion chamber defined by a top surface of said piston and an inner surface of said cylinder,   a device for providing a gas seal between an outer circumferential surface of said piston and said inner surface of said cylinder, which comprises, a piston ring, and   a piston ring groove formed in said outer circumferential surface of said piston for fitting said piston ring therein, in which   said piston ring groove is in the shape of an L-shaped keystone, including an annular outer portion disposed radially outwardly of said piston and parallel to the center axis of said piston, and   an annular wedged-shaped portion contiguous with said annular outer portion, extending toward the center axis of said piston and tapered toward the center axis of said piston when viewed in a vertical section,     said piston ring groove formed in a position in the outer circumferential surface of said piston that is remote from the top surface of said piston to form a top land in a peripheral portion of said piston, of substantial thickness extending in the direction of the center axis of said piston,   said piston ring is in the shape of an L-shaped keystone, including an annular outer ring portion disposed in said outer groove portion of said piston ring groove, extending parallel to the center axis of said piston, and   an annular wedge-shaped ring portion disposed in said wedge-shaped groove portion of said piston ring groove, tapering toward the center of axis of said piston when viewed in a vertical section, said annular wedge-shaped ring portion maintained in sliding contact at its outer circumferential surface with the inner surface of said cylinder,       with a gap defined between said L-shaped keystone piston ring and said L-shaped keystone piston ring groove, in which said top land has a diameter smaller than a diameter of a bottom land formed on the outer circumferential surface of said piston on a side of said piston ring groove opposite said top land, forming a gap between an outer circumferential surface of said top land and the inner surface of said cylinder, the diameter of said top land gradually expanding in the direction toward said piston ring groove away from said combustion chamber, said top land partially overlying said piston ring, and the outer circumferential surface of said top land curves inwardly from a maximum diameter at the edge of said piston ring groove toward the center axis of said piston in the direction toward said combustion chamber away from said piston ring groove, to allow gas pressure to be introduced from said combustion chamber into the gap defined between said L-shaped keystone piston ring and said L-shaped keystone piston ring groove.